1. Field of the Invention
The present invention relates to a power supply apparatus configured to supply a power supply voltage or a power supply current to a device.
2. Description of the Related Art
A test apparatus includes a power supply apparatus configured to supply a power supply voltage or a power supply current to a device under test (DUT). FIG. 1 is a block diagram showing a schematic configuration of a power supply apparatus investigated by the present inventors. A power supply apparatus 1100 includes a power supply output unit 1026, and a frequency controller (which will be referred to as the “controller” hereafter) 1024 configured to control the power supply output unit 1026. For example, the power supply output unit 1026 is configured as an operational amplifier (buffer), a DC/DC converter, a linear regulator, or otherwise as a constant current source, and is configured to generate a power supply voltage or a power supply current (hereafter power supply signal SPS) to be supplied to the DUT 1.
The power supply apparatus 1100 is configured to be capable of switching its mode between a voltage supply mode (VS) in which the voltage value VDD of the power supply signal SPS supplied to the DUT 1 is maintained at a constant value, and a current supply mode (IS) in which the current value IDD of the power supply signal is maintained at a constant value.
The controller 1024 is configured to output a control value such that the difference between the measurement value (value to be measured) which is a feedback value and a predetermined reference value (standard value) becomes zero. Examples of such a measurement value include a power supply voltage VDD supplied to the DUT 1, and a feedback signal VM that corresponds to the power supply current IDD.
In order to detect the current IDD in the current supply mode or in the voltage supply mode, a detection resistor Rs and a sense amplifier 1028 are arranged. The detection resistor Rs is arranged on a path of the power supply signal SPS. A voltage drop (detection voltage Vs) occurs between both terminals in proportion to the current IDD. The sense amplifier 1028 is configured to amplify the detection voltage Vs so as to generate the measurement value VM—I.
A selector 1030 is configured to select the measurement value VM—V of the voltage VDD in the voltage supply mode, and to select the measurement value VM—I of the current IDD in the current supply mode.
For example, a circuit component 1022 represented by a subtractor symbol shown in FIG. 1 is configured as an error amplifier (operational amplifier), and is configured to amplify the difference between the measurement value and the reference value. The analog controller 1024 is configured to generate the control value such that this difference becomes zero. The state of the power supply output unit 1026 is feedback controlled according to the control value. As a result, the power supply voltage VDD or otherwise the power supply current IDD, which is used as a value to be controlled, is stabilized to the reference value.
A selector 1032 is configured to receive the two measurement values VM—I and VM—V. Furthermore, the selector 1032 is configured to select the measurement value VM—I in the voltage supply mode, and to select the measurement value VM—V in the current supply mode. The A/D converter 1034 is configured to convert the measurement value selected by the selector 1032 into a digital value. The A/D converter 1034 functions as an ammeter in the voltage supply mode, and functions as a voltmeter in the current supply mode.